Frame construction for a vehicle

ABSTRACT

Abstract of the Disclosure 
         
   A frame assembly is described including a tunnel, an engine cradle disposed forward of the tunnel and connected thereto, and a sub-frame disposed forward of the engine cradle and connected thereto.  A forward support assembly extends upwardly from the subframe.  An upper column extends upwardly from the engine cradle to connect with the forward support assembly.  A rear brace assembly extends upwardly from the tunnel to connect with the forward support assembly and the upper column.  In one embodiment, the frame assembly further includes an engine disposed in the engine cradle.  An endless track is operatively connected to the engine and disposed beneath the tunnel for propulsion.  A pair of skis is operatively connected to a steering device for steering.  In another embodiment, the frame assembly further includes an engine disposed in the engine cradle.  A rear wheel is operatively connected to the engine and disposed beneath the tunnel for propulsion, and two front wheels are operatively connected to a steering device for steering.

Detailed Description of the Invention Cross Reference to RelatedApplications

[0001] This application claims priority to United States Application No.60/237,384, filed October 4, 2000, the entire contents of which areincorporated herein by reference. This application is acontinuation-in-part of United States Application No. 09/472,133,entitled "IMPROVED VEHICLE" filed on December 23, 1999, the contents ofwhich are incorporated herein by reference. U.S. Application 09/472,133and this application claim priority to Canadian Patent Application No.2,256,944, filed December 23, 1998, the entire contents of which areincorporated herein by reference. This application also incorporates byreference United States Application No. 09/472,134, entitled"SNOWMOBILE," filed December 23, 1999. Finally, this application isrelated to and incorporates by reference the entire contents of UnitedStates Patent Application Serial No. 60/230,432, entitled "A NOVELTHREE-WHEELED VEHICLE," filed September 6, 2000.

Background of the Invention

[0002]

Field of the Invention

[0003] The present invention relates to the construction of vehiclessuch as snowmobiles, all terrain vehicles ("ATVs"), and other similarvehicles. More specifically, the present invention concerns theconstruction of a frame and related structural elements that enhance theruggedness and ability of such vehicles to operate across a wide varietyof different terrains and under a wide variety of conditions. Inaddition, the present invention concerns the design and construction ofa frame for snowmobiles, ATVs, and related vehicles that facilitate theconstruction of such vehicles with an improved rider positioning.

Description of the Related Art

[0004] Snowmobiles, ATVs, and related vehicles (hereinafter,"recreational vehicles," although the appellation should not beconstrued to be limited only to the vehicles or type of vehiclesdescribed herein) often function under similar operating conditions.Despite this, snowmobiles, ATVs, and other recreational vehicles oftendo not share a common design approach or a commonality of components.This is due, in large part, to the different stresses and strains(mainly at the extremes) that the different vehicles experience duringroutine operation.

[0005] Specifically, snowmobiles are designed with frame assemblies andsuspensions that easily absorb the shock of obstacles encountered ongroomed trails and in deep snow. They are also designed to handle theforces generated when the snowmobile is driven aggressively (e.g., underracing conditions). In addition, their frame assemblies are designed toprovide optimum steering and performance in snow, whether on groomedsnowmobile trails (packed snow) or in ungroomed, off-trail areas (powderor natural snow).

[0006] ATVs, on the other hand, are designed with suspensions and frameassemblies that are expected to absorb the type of momentarily intenseforces associated with more rugged terrain, specifically of the typeencountered in forests and woodland environments. In addition, an ATVframe is designed to withstand forces associated with significanttorsional stresses that are typical when an ATV straddles large objectsor when the wheels are disposed at different elevations because of theextreme terrain in which the ATV often operates.

[0007] It should be kept in mind that the design parameters of the frameassemblies for these two vehicles are also different. In a snowmobile,the frame at the rear of the vehicle is only about 15 inches wide. Thisis sufficient to cover the endless track that propels the vehicle and toprovide a seating area for the driver. The narrow width, however,imposes certain design restrictions on the vehicle. ATVs, on the otherhand, are designed with a significantly wider base, which is typically50 inches or more. This width also imposes certain design restrictionson the ATV.

[0008] Snowmobiles and ATVs are also designed with different centers ofgravity. In the typical snowmobile, the center of gravity is very low.This assists the snowmobile rider when he or she is on a slope or in aturn because the snowmobile will naturally resist the tendency to leanor tip. ATVs, on the other hand, like off-road trucks and the like, areexpected to traverse taller objects. Accordingly, their frames aredesigned so that the engine and seating area is further from the groundthan a snowmobile. Thus, ATVs have higher centers of gravity.

[0009] Naturally, since both vehicles are designed with off-road use inmind, there are similarities between the two. Both are provided withrugged frames. Moreover, both are provided with strong suspensions.Despite this, there have been few vehicles designed that capitalize onthese similarities.

[0010] Recognizing this basic similarity between the two vehicles, someafter-market designers have developed kits that permit snowmobiles to beconverted to ATVs and vice-versa. However, such kits are limited intheir effectiveness because the two vehicles are so completely differentfrom one another in their basic designs. The resulting, convertedvehicles suffer from drawbacks that are associated with the purpose forwhich the primary vehicle was designed. For example, a snowmobileconverted to an ATV is not expected to be able to traverse the same typeof terrain as a pure ATV. Similarly, an ATV that has been converted to asnowmobile is not expected to be able to traverse the same terrain thata pure snowmobile can.

[0011] Partly due to the consumer's use of snowmobiles in the winter andATVs in the summer, the evolution of both snowmobiles and ATVs hasconverged in recent years. Also, in recent years, designers have begunto apply the same basic design concepts to both vehicle types. What hasresulted is a recognition that vehicles may be designed that incorporatemany of the same structural elements and follow very similar designapproaches.

[0012] The basis for the present invention stems from this basicrecognition.

Summary of the Invention

[0013] It is, therefore, an object of the present invention to provide aframe assembly with a tunnel, an engine cradle disposed forward of thetunnel and connected thereto, and a sub-frame disposed forward of theengine cradle and connected thereto. The frame assembly further includesa forward support assembly extending upwardly from the subframe, anupper column extending upwardly from the engine cradle to connect withthe forward support assembly, and a rear brace assembly extendingupwardly from the tunnel to connect with the forward support assemblyand the upper column.

[0014] It is another object of the present invention to provide a frameassembly wherein the forward support assembly, the upper column, and therear brace assembly connect at an apex above the upper column.

[0015] Another object of the present invention is to provide a frameassembly where the forward support assembly and the rear brace assemblyform a pyramidal construction.

[0016] A further object of the present invention is to provide a frameassembly further including a steering bracket connected at the apex forsupporting a steering shaft at its upper end. In an alternateembodiment, the steering bracket may include a plurality of pairs ofholes for positioning of the steering shaft in a plurality of positions.

[0017] One other object of the present invention is to provide a frameassembly that also includes an engine disposed in the engine cradle andan endless track operatively connected to the engine and disposedbeneath the tunnel for propulsion. In this embodiment, a pair of skisare operatively connected to a steering device for steering.

[0018] Still another object of the present invention is to provide aframe assembly with an engine disposed in the engine cradle and a rearwheel operatively connected to the engine and disposed beneath thetunnel for propulsion. In this embodiment, two front wheels operativelyconnected to a steering device for steering.

[0019] It is yet another object of the present invention to provide aframe assembly for a vehicle that includes a tunnel and an engine cradleadapted to receive an engine therein. A rear brace assembly is attachedto the tunnel at a point between its front and rear ends and extendsupwardly therefrom. A forward support assembly is attached to the rearbrace assembly and extends forwardly and downwardly therefrom. In afurther variation of this frame assembly, the rear brace assemblycomprises a left and a right leg and the forward support assemblycomprises a left and a right leg. The left and right legs of the rearbrace assembly and the forward support assembly connect to one anotherat an apex to form a pyramidal structure above the tunnel and enginecradle.

[0020] Still other objects of the present invention will be madeapparent by the discussion that follows.

Brief Description of Drawings

[0021] The invention will be more fully described in conjunction withthe following drawings wherein:

[0022]Figure 1 is a side-view schematic illustration of a prior artsnowmobile, showing the prior art positioning of a rider thereon;

[0023]Figure 2 is a side view illustration of the exterior of asnowmobile constructed according to the teachings of the presentinvention, also showing the positioning of a rider thereon;

[0024]Figure 3 is an overlay comparison between the a prior artsnowmobile (of the type depicted in Figure 1) and a snowmobileconstructed according to the teachings of the present invention (asshown in Figure 2), illustrating the difference in passengerpositioning, among other features;

[0025]Figure 4 is an exploded view of a frame assembly representative ofthe type of construction typical of a snowmobile assembled according tothe teachings of the prior art (specifically, the view illustrates thecomponents of a 2000 model year Ski-Doo®Mach™ Z made by Bombardier Inc.of Montréal, Québec, Canada);

[0026]Figure 5 is a side view schematic illustration of the snowmobileillustrated in Figure 2, with the fairings and external details removedto show some of the internal components of the snowmobile and theirpositional relationship to one another;

[0027]Figure 6 is a perspective illustration of a portion of the frameassembly of the present invention, specifically the portion disposedtoward the rear of the vehicle;

[0028]Figure 7 is a perspective illustration of a forward support frame,which connects with the portion of the frame assembly depicted in Figure6;

[0029]Figure 8 is a front view illustration of an upper column of theframe assembly shown in Figure 6;

[0030]Figure 9 is a left side view illustration of the upper columndepicted in Figure 8;

[0031]Figure 10 is a right side view illustration of the upper columnshown in Figure 8;

[0032]Figure 11 is a perspective illustration, from the front left side,of a tunnel portion of the frame assembly of the present invention;

[0033]Figure 12 is another perspective illustration, from the rear leftside, of the tunnel portion of the present invention shown in Figure 11;

[0034]Figure 13 is a perspective illustration, from the front left side,showing the combination of the frame assembly depicted in Figure 6connected to the tunnel portion depicted in Figures 11 and 12;

[0035]Figure 14 is a perspective illustration, from the rear left side,showing the combination of the frame assembly depicted in Figure 6connected to the tunnel portion depicted in Figures 11 and 12 and alsoshowing a portion of a front suspension assembly;

[0036]Figure 15 is a perspective illustration, from the front left side,of some of the components that are part of the front suspension assemblydepicted in Figure 14;

[0037]Figure 16 is a perspective illustration, from the front left side,of a portion of a sub-frame that is part of the front suspensionassembly illustrated in Figure 15;

[0038]Figure 17 is another perspective illustration, from the front leftside, of the front suspension assembly for a snowmobile, constructedaccording to the teachings of the present invention, showing thepositional relationship between the parts illustrated in Figure 15 andthe sub-frame illustrated in Figure 16;

[0039]Figure 18 is a side view schematic of the frame assembly of thepresent invention showing the positional relationship between the frameassembly and the engine, among other components;

[0040]Figure 19 is a perspective illustration, from the left side, ofthe frame assembly according to the teachings of the present invention,also showing the positional relationship between the frame assembly, theengine, and the front suspension;

[0041]Figure 20 is another perspective illustration, from the front leftside, of the combined frame assembly and tunnel portion constructedaccording to the teachings of the present invention, also showing thepositional relationship between the frame assembly, the engine, and thefront suspension;

[0042]Figure 21 is a front perspective illustration of the embodimentdepicted in Figure 20;

[0043]Figure 22 is a perspective illustration of a slightly differentembodiment from the one depicted in Figure 20;

[0044]Figure 23 is a schematic side view illustration of the frameassembly of the present invention as embodied in a wheeled vehicle;

[0045]Figure 24 is a schematic side view illustration of the frameassembly of the present invention as embodied in a slightly modifiedversion of a wheeled vehicle;

[0046]Figure 25 is an enlarged side view illustration of the frameassembly of the present invention as embodied in the wheeled vehicleshown in Figure 24;

[0047]Figure 26 is a perspective illustration, from the left rear, ofthe frame assembly of the present invention, showing some of the detailof the front suspension incorporated into the wheeled vehicle shown inFigures 23 and 24;

[0048]Figure 27 is a perspective illustration, from the front left,showing the frame assembly of the present invention as depicted inFigure 26;

[0049]Figure 28 is a perspective illustration, from the rear left sideof an alternate embodiment of the frame assembly of the presentinvention;

[0050]Figure 29 is a side view illustration of the frame assembly shownin Figure 28;

[0051]Figure 30 is a top view of the frame assembly depicted in Figure28;

[0052]Figure 31 is a side view illustration of the frame assembly shownin Figure 29, illustrating the variable positioning of the handlebarsthat is possible with this embodiment of the present invention;

[0053]Figure 32 is a perspective illustration of the embodiment shown inFigure 31, showing in greater detail the variations in positioning ofthe handlebars that is made possible by the construction of the presentinvention;

[0054]Figure 33 is a close-up side-view detail of the connection pointbetween the handlebars and the frame assembly of the present invention,illustrating the variable positioning of the handlebars;

[0055]Figure 34 is a further illustration of the variable positioningfeature of the present invention; and

[0056]Figure 35 is a graph showing the vertical displacement rate of theframe of the present invention in comparison with a prior art Bombardiersnowmobile (the ZX™ series) and a prior art snowmobile made by ArcticCat.

Detailed Description

[0057] Before delving into the specific details of the presentinvention, it should be noted that the conventions "left," "right,""front," and "rear" are defined according to the normal, forward traveldirection of the vehicle being discussed. As a result, the "left" sideof a snowmobile is the same as the left side of the rider seated in aforward-facing position on the vehicle (or travelling in a forwarddirection on the vehicle).

[0058]Figure 1 illustrates a rider operator 10 sitting on a prior artsnowmobile 12. Rider 10 is positioned on seat 14, with his weightdistributed over endless track 16. Motor 18 (shown in general detail) islocated over skis 20. As with any snowmobile, endless track 16 isoperatively connected to motor (or engine) 18 to propel snowmobile 12over the snow. Motor or engine 18 typically is a two-stroke internalcombustion engine. Alternatively, a 4-stroke internal combustion enginemay be substituted therefor. In addition, any suitable engine may besubstituted therefor.

[0059]Figure 2 provides a side view of a snowmobile 22 constructedaccording to the teachings of the present invention. Here,rider/operator 24 is shown in a more forward, motor cross racing-likeposition, which is one of the aspects of the present invention. In thisposition, the weight of operator 24 is forward of the position of rider10 in the prior art example.

[0060] The positioning of rider 24 closer to motor 36 offers severaladvantages that are not achieved by the prior art. For example, sincerider 24 is positioned closer to the engine 36, the center of gravity ofrider 24 is closer to the center of gravity of the vehicle, which isoften at the drive axle of the vehicle or near thereto. In other words,rider 24 has his weight distributed more evenly over the center ofgravity of the vehicle. As a result, when the vehicle traverses roughterrain, rider 24 is better positioned so that he does not experiencethe same impact from an obstacle as rider 10 on snowmobile 12. Theimproved rider positioning illustrated in Figure 2 also improves therider's ability to handle the vehicle.

[0061]Figure 2 illustrates the basic elements of snowmobile 22.Snowmobile 22 includes an endless track 26 at its rear for propulsion. Arear suspension 28 connects endless track 26 to the vehicle frame.Snowmobile 22 also includes a front suspension 30. Skis 32, which areoperatively connected to handlebars 34, are suspended from the frontsuspension 30 for steering the vehicle. A motor or engine (preferably,an internal combustion engine) 36 is located at the front of snowmobile22, above skis 32. Operator 24 is seated on a seat 38, which ispositioned above the endless track 26.

[0062] Three positional points of particular relevance to the presentinvention are also shown in Figure 2. Specifically, seat position 40,foot position 42, and hand position 44 of operator 24 are shown. In themodified seating position of operator 24, which is made possible by theteachings of the present invention, hand position 44 is forward of footposition 42, which is forward of seat position 40. The three positionsdefine three angles, a, b, and c between them that help to define theseating position of operator 24, which permits rider 24 to be closer tocenter of gravity 45 of the vehicle. Moreover, hand position 44 isforward of center of gravity 45 of snowmobile 22.

[0063]Figure 3 provides an overlay between prior art snowmobile 12 andsnowmobile 22 constructed according to the teachings of the presentinvention. Rider 10 (of prior art snowmobile 12) is shown in solid lineswhile operator 24 (of snowmobile 22) is shown in dotted lines forcomparison. The comparative body positions of rider 10 and operator 24are shown. As is apparent, the present invention permits theconstruction of a snowmobile 22 where the rider 24 is in a more forwardposition. Moreover seat position 40, foot position 42, and hand position44 differ considerably from seat position 46, foot position 48, and handposition 50 in the prior art snowmobile 12. In this position, the centerof gravity of operator 24 is closer to center of gravity 45 ofsnowmobile 22 than in the prior art example.

[0064] As a basis for comparison with the figures that provide thedetails of the present invention, Figure 4 provides an exploded view ofa frame assembly 52 for a snowmobile constructed according to theteachings of the prior art. Frame assembly 52 includes, as its majorcomponents, a tunnel 54 and an engine cradle 56. As illustrated, enginecradle 56 is positioned in front of tunnel 54. Engine cradle 56 receivesmotor 18.

[0065] As shown in Figure 4, tunnel 54 is basically an inverted U-shapedstructure with a top plate 58 integrally formed with left and right sideplates 60, 62, respectively. Top plate 58 provides the surface onto withseat 14 is mounted, as would be known to those skilled in the art. Footboards 64 (of which only the left foot board is visible in Figure 4) areintegrally formed with the side plates 60, 62 and extend outwardly,perpendicular to the plane of side plates 60, 62. Foot boards 64 providea location on which rider 10 may place his feet during operation ofsnowmobile 12. While top plate 58, side plates 60, 62, and foot boards64 are preferably formed from aluminum, any suitable alternativematerial may be used, as would be recognized by those skilled in theart. Moreover, while top plate 58, side plates 60, 62 and footboards 64are shown as an integral structure, an integral construction is notrequired. Instead, top plate 58, side plates 60, 62, and foot boards 64may be separately manufactured and connected to one another by anysuitable means known in the art.

[0066]Figure 4 also shows that engine cradle 56 is connected to tunnel54 by any suitable means known to those skilled in the art. For example,engine cradle 56 may be welded or bolted to tunnel 54. Engine cradleincludes a bottom plate 66 and left and right side walls 68, 70, whichare provided with left and right openings 72, 74, respectively. Leftopening 72 is provided so that the shafts for the transmission(typically a continuously variable transmission or CVT) may extendoutwardly from left wall 68. The shafts that connect the engine 18 tothe transmission pass through left opening 72. A gearbox (not shown)typically is provided on the right side of snowmobile 10. The shaftsthat connect engine 18 to the gearbox pass through right opening 74.Left and right openings 72, 74 also allow heat from engine 18 to beradiated from engine cradle 56, which assists in cooling engine 18.

[0067] As Figure 4 illustrates, left side wall 68 is provided with abeam 76 that is removably connected thereto. Beam 76 may be removedduring servicing, for example, to facilitate access to the enginecomponents and peripheral elements disposed within left opening 72.

[0068]Figure 4 also illustrates the placement of a handlebar supportelement 78, which connects to the rear of engine cradle 56. Handlebarsupport element 78 is generally an inverted U-shaped structure thatextends upwardly from the combined engine cradle 56 and tunnel 54. Abracket 80 is positioned at the midpoint of handlebar support element 78and provides structural support for handlebars 82, which is used tosteer snowmobile 12.

[0069] To provide an improved driver positioning, as described above,the inventors of the present invention appreciated the advantages ofmoving handlebars 82 forward of the position shown in Figure 1. To dothis, however, required a novel approach to the construction of frameassembly 52 of snowmobile 12. The redesign resulted in the presentinvention, which is described in detail below.

[0070] As illustrated in Figure 5, snowmobile 22 incorporates acompletely redesigned frame assembly 84. Frame assembly 84 includes,among other elements, tunnel 86, engine cradle 88, and over-archingframe elements 90. As with snowmobile 12, snowmobile 22 includes a seat94 on which rider 24 sits while operating snowmobile 22. Tunnel 86 isconnected to a rear suspension 96 that contains a number of wheels 98disposed on a slide frame 100 around which an endless track 102 rotatesto propel snowmobile 22 across the snow.

[0071] Endless track 102 is connected to engine 104 (preferably a two orfour stroke internal combustion engine) positioned within engine cradle88. Endless track 102 is connected to engine 104 through a transmission106, which is preferably a continuously variable transmission (or"CVT"), as is known in the art.

[0072] Two skis 108 are provided at the front of snowmobile 22 forsteering. Skis 108 are connected to engine cradle 88 through a frontsuspension 110. Front suspension 110 connects to skis 108 through apivot joint 112 on the top of skis 108. Skis 108 are operativelyconnected to a steering shaft 114 that extends over engine 104. Steeringshaft 114 is connected, in turn, to handlebars 116, which are used byoperator 24 to steer snowmobile 22.

[0073]Figure 6 illustrates the individual elements of rear frameassembly 84 in greater detail. Rear frame assembly 84 includes an uppercolumn 118, which is an inverted U-shaped structural element. Ifnecessary, upper column 118 may be reinforced with a cross-member 120,but this is not needed to practice the present invention. A left brace122 and a right brace 124 are connected to a bracket 126 above uppercolumn 118. A bushing or bearing (or other similar element) 128 isattached to bracket 126 and accepts steering shaft 114 therethrough. Italso secures steering shaft 114 to rear frame assembly 84. Left andright braces 122, 124 include left and right brackets 130, 132 at theirlower portions. Left and right brackets 130, 132 secure left and rightbraces 122, 124 to tunnel 86 of snowmobile 22.

[0074] It should be noted that, while the construction of frame assembly84 is illustrated involves the use of tubular members, frame assembly 84may also be constructed according to a monocoque or pseudo-monocoquetechnique. A monocoque construction is one where a single sheet ofmaterial is attached to an underlying frame (such as with theconstruction of an aircraft). The skin applied to the frame addsrigidity to the underlying frame structure. In a similar manner, apseudo-monocoque technique provides a rigid structure by providing aframe constructed from a single sheet of material.

[0075] Instead of constructing frame assembly 84 from a number oftubular members, frame assembly 84 may be constructed from a singlesheet of material (such as aluminum) that has been pressed or moldedinto the appropriate shape using a pseudo-monocoque manufacturingtechnique. As would be understood by those skilled in the art, thiswould result in a construction that has a high strength with a lowweight.

[0076]Figure 7 illustrates a forward support assembly 134 (also calledfront triangle 134), which connects to bracket 126 and extends forwardlyof bracket 126. Forward support assembly 134 includes a bracket 136 atits rear end that connects to bracket 126 of frame assembly 84(preferably bolted). Forward support assembly 134 also has left andright braces 138, 140 that extend forwardly and downwardly from bracket136 and are connected thereto preferably by welding. Left and rightbraces 138, 140 are connected at their forward ends by a cross-member142, which includes a plurality of holes 144 therein to lighten theweight thereof. Left and right connecting brackets 145, 146 areconnected to cross-member 142. The left and right connecting brackets145, 146 connect, in turn, to front suspension 110.

[0077]Figure 8, 9, and 10 illustrate upper column 118 in greater detail.As described above, upper column 118 is essentially an inverted U-shapedmember that is preferably tubular in shape to facilitate itsconstruction. Upper column 118 preferably is bent into the appropriateshape from a straight tube with the dimensions shown. As would beunderstood by those skilled in the art, however, upper column 118 neednot be made as a tubular member.

[0078] Upper column 118 has left and right legs 148, 150 that extenddownwardly from an apex 152. A bracket 154 is disposed at apex 152 forconnection to bracket 126 of frame assembly 84. Preferably, bracket 154is welded at the apex of upper column 118 (however any other suitableattachment means is possible). Left leg 148 includes a bracket 156 atits lower-most portion that connects left leg 148 to engine cradle 88.Similarly, right leg 150 includes a bracket 158 at its lower-mostportion to connect right leg 150 to engine cradle 88. Preferably,brackets 156, 158 are welded to upper column 118. Left and right legs148, 150 preferably attach to engine cradle 88 via bolts or othersuitable fasteners.

[0079] Figures 11 and 12 illustrate tunnel 86 in greater detail. Tunnel86 includes a top plate 160 with left and right downwardly extendingside plates 162, 164. A left foot rest 166 extends outwardly from thebottom of left side plate 162. Similarly, a right foot rest 168 extendsoutwardly from the bottom portion of right side plate 164. Left andright foot rests 166, 168 provide a location along tunnel 86 onto whichrider 24 may place his or her feet while operating snowmobile 22.

[0080] Left side plate 162 extends forwardly beyond the front portion170 of tunnel 86 to form a left engine cradle wall 172. Similarly, rightside plate 164 extends forwardly of front end 170 of tunnel 86 to formright engine cradle wall 174. At the lower edge of left and right enginecradle walls 172, 174, there are laterally extending portions 176, 178,which serve to strengthen left and right engine cradle walls 172, 174.Removable elements 180 extend between left foot rest 166 and leftlaterally extending portion 176. Removable portions 180 may or may notbe removed between left foot rest 166 and left laterally extendingportion 176. Figure 11 shows removable portions 180 removed, whileFigure 12 shows removable portions 180 not removed. It should be notedthat the same removable portions 180 may or may not extend between rightfoot rest 168 and right laterally extending portion 178.

[0081] Left engine cradle wall 172 preferably includes an opening 182therethrough. Opening 182 permits the shafts from transmission 106 topass therethrough. Unlike left engine cradle wall 172, right enginecradle wall 174 does not include such an opening. Instead, right enginecradle wall 174 is essentially solid. Due to its construction, rightengine cradle wall 174 reflects radiant heat from engine 104 back toengine 104 to assist in minimizing heat dissipation from engine 104.Left and right openings 184, 186 are provided through left and rightengine cradle walls 172, 174 so that a drive shaft 188 may passtherethrough. Drive shaft 186 connects to endless track 102 forpropulsion of snowmobile 22. Opening 182 may include a member 189 aboutits periphery, also as illustrated in Figures 11 and 12, that providesclearance for the engine. Left engine cradle wall 172 also includes anopening 192 above opening 184 through which a shaft passes for part oftransmission 106.

[0082] Figures 13 and 14 illustrate a combination of a variation offrame assembly 190 connected to tunnel 86. Frame assembly 190 includesupper column 118 as illustrated in Figures 8-10. However, frame assembly190 differs somewhat from frame assembly 84. For example, left and rightbraces 194, 196 are shaped so that they extend outwardly from thepositions defined by left and right braces 122, 124. As illustrated,left and right braces 194, 196 include elbows 198, 200. A cross-brace202 optionally may be placed between left and right braces 194, 196 toadd structural rigidity to frame assembly 190. As with frame assembly84, a bracket 126 is provided at apex 204 where left and right braces194, 196 meet one another. Forward support assembly 134 is the same asdepicted in Figure 7. A front engine cradle wall 206 is also shown inFigure 13.

[0083] Figures 15-17 illustrate various aspects of front suspension 110and associated structures. While the figures illustrate the embodimentpreferably used in combination with snowmobile 22, it should berecognized that front suspension 110 may also be used in combinationwith a wheeled vehicle, as will be discussed in connection with Figures23-27.

[0084] Front suspension 110 includes left and right ski legs 208, 210.Left and right ski legs 208, 210 are preferably made from aluminum andare preferably formed as extrusions. While an aluminum extrusion ispreferred for left and right ski legs 208, 210, those skilled in the artwould appreciate that ski legs could be made from any suitable materialand in any acceptable manner that would provide similar strength and lowweight characteristics. Left and right ski legs 208, 210 include holes212, 214 through which a fastener (not shown) is disposed to pivotallyconnect skis 32 to snowmobile 22, as shown in Figure 2.

[0085] Left and right ski legs 208, 210 are movably connected to leftand right support arms 216, 218. Left and right suspension arms 216, 218include lower left and right suspension support arms 220, 222 and upperleft and right suspension support arms 224, 226.

[0086] As shown in Figures 15 and 17, lower left suspension support arm220 connects to left ski leg at lower left attachment point 228preferably through a ball joint (not shown) so that left ski leg 208 maypivot and rotate with respect to lower left suspension support arm 220.Similarly, lower right suspension support arm 222 connects to right skileg 210 at lower right attachment point 230, preferably through a balljoint. Upper left suspension support arm 224 preferably attaches to leftski leg 208 at upper left attachment point 232, preferably through aball joint or other suitable means. In addition, upper right suspensionsupport arm 226 connects to right ski leg 210 at upper right attachmentpoint 234 through a ball joint or other suitable means.

[0087] Lower left suspension support arm 220 includes front and rearmembers 236, 238, which meet at apex 240 where they connect with leftlower eyelet 242. Front member 236 includes a joint 244 at an inner end,and rear member 238 includes a joint 246 also at an inner end.Similarly, lower right suspension support arm 222 includes front andrear members 248, 250, which meet at apex 252 where they connect withright lower eyelet 254. Front member 248 includes a joint 256 at aninner end and rear member 250 includes a joint 258 also at an inner end.

[0088] Upper left suspension support arm 224 includes front and rearmembers 260, 262, which meet at apex 264 where they connect with upperleft eyelet 266. Front member 260 includes a joint 268 at an inner end,and rear member 262 includes a joint 270 also at an inner end.Similarly, upper right suspension support arm 226 includes front andrear members 272, 274, which meet at apex 276 where they connect withupper right eyelet 278. Front member 272 includes a joint 280 at aninner end and rear member 274 includes a joint 282 also at an inner end.

[0089] At a point inward from apex 240, lower left suspension supportarm 220 includes a left bracket 284 that is connected to and extendspartially along front and rear members 236, 238. Similarly, lower rightsuspension support arm 222 includes a right bracket 286 that isconnected to and extends partially along front and rear members 248,250. Slidably attached to rear member 238 of lower left suspension arm220 is a left pivot block 288. A right pivot block 290 is slidablyattached to rear member 250 of lower right suspension support arm 222. Astabilizer bar 292 is connected between left and right pivot blocks 288,290. Stabilizer bar 292 is adapted to slide and pivot by way of left andright pivot blocks 288, 290. These blocks 288, 290 slide relative toleft and right lower suspension support arms 220, 222. Left and rightbushings 296, 298 are provided to allow some rotation of the componentsof front suspension 110. Left and right ski legs 208, 210 rotatablyconnect to front suspension 110 for facilitating movement of skis 32.

[0090]Figure 16 illustrates sub-frame 294, which is essentially aunitary, V-shaped structure. Sub-frame 294, which forms a part of frontsuspension 110, includes a central channel 300 flanked on either side byleft and right upwardly extending panels 302, 304. Left upwardlyextending panel 302 includes a left lower panel 306 connected to lefttransition structure 308 and left triangular panel 310. Similarly, rightupwardly extending panel 304 includes a right lower panel 312 connectedto right transition structure 314 and right triangular panel 316. Whilesub-frame 294 preferably is a unitary structure (an integrally-formedstructure), sub-frame 294 need not be constructed in this manner. Aswould be understood by those skilled in the art, sub-frame 294 may beassembled from a number of separate elements that are connected togetherby any suitable means such as by welding or by fasteners.

[0091] As illustrated in Figure 17, sub-frame 294 is an integral part offront suspension 110 and connects to left support arm 216 and rightsupport arm 218 through a number of brackets 318 connected at variouslocations on sub-frame 294.

[0092]Figure 18 is a side view of one embodiment of the completed frameassembly 84 of the present invention. As shown, over-arching frameelements 90 are connected between tunnel 86 and sub-frame 294 toestablish an apex 320 to which steering shaft 114 is connected.

[0093]Figure 19 is a perspective illustration of the embodiment of thepresent invention shown in Figures 13 and 14 to assist in understandingthe scope and content of the present invention. As illustrated, driveshaft 322 extends through left opening 182 in left engine cradle wall172. A portion of gearbox 324 is also visible. In addition, left shockabsorber 326, which is connected between cross-member 142 and leftsupport arm 216, is illustrated. Right shock absorber, which extendsbetween cross-member 142 and right support arm 218 is visible in Figure20. Furthermore, left forward foot wall 330 is shown at the forward endof left foot rest 166. A similar forward foot wall may be provided onthe right side of snowmobile 22 (but is not illustrated herein).

[0094] Figures 20 and 21 illustrate further details of the presentinvention by showing the various elements from slightly differentperspective views. Figure 22 illustrates the modified version of theelements of the present invention shown in Figures 6 and 7. Here, leftand right braces 122, 124 are illustrated instead of left and rightbraces 194, 196. As discussed previously, left and right braces 122, 124differ from left and right braces 194, 196 in that they are not bentbut, instead, are straight elements of overarching frame 90. The sameleft and right braces 122, 124 are shown in Figure 18. As would beunderstood by those skilled in the art, the two different embodiments ofthese braces are interchangeable. In addition, their shape may bealtered depending on the requirements of the particular vehicle design,as would be understood by those skilled in the art.

[0095] Left and right braces 194, 196 are bent to accommodate an airbox(not shown) between them. Left and right braces 122, 124 are not bentbecause they do not need to accommodate an airbox.

[0096]Figure 20 also illustrates steering gear box 115 at the bottom endof steering shaft 114 that translates the movement of handlebars 116into a steering motion of skis 32.

[0097] Figures 23-27 illustrate alternate embodiments of the presentinvention that are designed for a wheeled vehicle 332, rather than asnowmobile 22. For the most part, the elements designed for wheeledvehicle 332 are the same as those for snowmobile 22, except for thoseelements required to attach wheels 334 to wheeled vehicle 332.

[0098] In the preferred embodiment of wheeled vehicle 332, the vehicleincludes two front wheels 334 and a single rear wheel 336. As would beunderstood by those skilled in the art, however, wheeled vehicle 332 maybe constructed with two rear wheels rather than one. If so, wheeledvehicle 332 would be a four-wheeled vehicle rather than thethree-wheeled vehicle shown.

[0099] Wheeled vehicle 332 includes a seat 338 disposed over tunnel 86in the same manner as snowmobile 22. The vehicle includes engine 104 atits forward end, encased by fairings 340. Fairings 340 protect engine104 and provide wheeled vehicle 332 with an aesthetically pleasingappearance. Engine 104 is connected to CVT 106, which translates thepower from engine 104 into motive power for wheeled vehicle 332.

[0100] As shown in Figure 23, CVT 106 is connected by suitable means todrive shaft 342, which is connected to rear wheel 336 by a drive chain344. A sprocket 346 is connected to drive shaft 342. A similar sprocket348 is provided on the shaft connected to rear wheel 336. Drive chain344 is an endless chain that connects sprockets 346, 348 to one another.To stop wheeled vehicle 332 during operation, disc brakes 350 areconnected to front wheels 334. Disc brakes 350 clamp onto discs 352 toslow or stop wheeled vehicle 332 in a manner known to those skilled inthe art.

[0101] A rear suspension 354 is provided under tunnel 86. Rearsuspension 354 absorbs shocks associated with the terrain over whichwheeled vehicle 332 travels. Rear suspension 354 replaces rearsuspension 28 on snowmobile 22.

[0102]Figure 24 illustrates an alternate embodiment of wheeled vehicle356. Wheeled vehicle 356 differs in its construction at the rear.Specifically, rear end 358 is shorter than that shown for wheeledvehicle 332. In addition, wheeled vehicle 356 includes a four strokeengine, rather than the two stroke engine 104 illustrated for wheeledvehicle 332. Also, wheeled vehicle 356 includes a manual speedtransmission 360 (with a clutch) rather than continuously variabletransmission 106, as illustrated with other embodiments of the presentinvention. Both constructions of the wheeled vehicle, as well as manyother variations, are contemplated within the scope of the presentinvention. In addition, as discussed above, the present invention may beused with a two or four stroke engine (or any other type of engine thatprovides the motive power for the vehicle).

[0103]Figure 25 illustrates in greater detail the embodiment of thepresent invention shown in Figure 24.

[0104] Figures 26-27 illustrate the basic frame assembly contemplatedfor wheeled vehicles 332, 356. For either vehicle, the construction offrame assembly 191 is similar to that previously described. Thisembodiment differs in that left and right wheel knuckles 366, 368 areprovided so that wheels 334 may be attached thereto. In most otherrespects, the construction of frame assembly 191 is the same as thatpreviously described.

[0105] The variable geometry of steering shaft 364 will now be describedin connection with Figures 28-34.

[0106] As illustrated in Figure 28, left brace 122 and right brace 124extend upwardly from tunnel 370 to apex 372 where they connect tovariable geometry steering bracket 374. Upper column 118 extends fromleft engine cradle wall 376 and right engine cradle wall 174 and alsoconnects to variable geometry steering bracket 374. Forward supportassembly 134 extends from sub-frame 294 to variable geometry steeringbracket 374.

[0107] Variable geometry steering bracket 374 is essentially a U-shapedelement with a rear end 376 and a forward end 378. At rear end 376, afirst cross-member 380 extends between left and right legs 382, 384 ofvariable geometry steering bracket 374 to define a closed structure. Asecond cross member 386 extends between left and right legs 382, 384forward of first cross member 380 and defines a U-shaped opening 387toward forward end 378 of variable geometry steering bracket 374. Afirst pair of holes 388 and a second pair of holes 390 are disposedthrough left and right legs 382, 382 of variable geometry steeringbracket 374 and provide separate attachment points for steering shaft364. Figure 29 illustrates the same structures in side view and Figure30 illustrates the same structures in top view.

[0108] This embodiment of the frame assembly of the present inventiondiffers from the previous embodiments in a few respects. First, leftengine cradle wall 393 includes a C-shaped opening 392 instead ofopening 182. C-shaped opening 392 facilitates maintenance of an engine(not shown) in engine cradle 394. Second, an elongated radiator 396 isintegrated into tunnel 370. Radiator 396 includes an inlet 398 and anoutlet 400 that are connected to the cooling system of the engine toassist in reducing the temperature of the coolant therein. To facilitatedissipation of heat, radiator 396 includes fins 402 on its underside.

[0109]Figure 31 provides another side view of the frame assembly of thepresent invention and illustrates the two positions of steering shaft364 made possible by the construction of variable geometry steeringbracket 374. To accommodate the variable geometry of steering shaft 362and handlebars 116, steering shaft 364 includes a bend 402 at its lowerend. Steering shaft 364 passes through a bearing or bushing (not shown)at its upper end that is connected to variable geometry steering bracket374 at either of first or second pairs of holes 388, 390. By selectingeither first or second pairs of holes 388, 390, first and secondhandlebar positions 404, 406 are selectable. As would be recognized bythose skilled in the art, however, variable geometry steering bracket374 may be provided with greater that two pairs of holes 388, 390 tofurther increase the variability handlebars 116. Also, variable geometrysteering bracket 374 may be provided with a construction that permitsinfinite variation of the position of handlebars, as would be understoodby those skilled in the art, should such a construction be desired.

[0110] Figures 32-34 provide additional views of the variablepositioning of the handlebars 116 to facilitate an understanding of thescope of the present invention.

[0111] Frame assembly 84, 190, 191 of the present invention uniquelydistributes the weight loaded onto the vehicle, whether it is snowmobile22 or one of wheeled vehicles 332, 356. Each of the main components ofthe frame assembly 84, 190, 191 forms a triangular or pyramidalconfiguration. All of the bars of the frame assembly 84, 190, 191 workonly in tension and compression, without bending. Therefore, each bar offrame assembly 84, 190, 191 intersects at a common point, the bracket126 (in the non-variable steering geometry) or variable geometrysteering bracket 374. With this pyramidal shape, the present inventioncreates a very stable geometry.

[0112] Specifically, the structure of frame assembly 84, 190, 191enhances the torsional and structural rigidity of the frame of thevehicle. This improves handling. Usually, with a snowmobile, there isonly a small torsional moment because the width of the snowmobile isonly about 15 inches. An ATV, on the other hand, has a width of about 50inches and, as a result, experiences a significant torsional moment.Therefore, to construct a frame assembly that is useable in either asnowmobile or an ATV, the frame must be able to withstand the torsionalforces associated with an ATV.

[0113] Not only does frame assembly 84, 190, 191 reduce torsionalbending, it also reduces the bending moment from front to rear. Theincreased rigidity in both directions further improves handling.

[0114] In addition, the creation of frame assembly 84, 190, 191 has atleast one further advantage in that the frame can be made lighter andstronger than prior art frame assemblies (such as frame assembly 52,which is illustrated in Figure 4). In the conventional snowmobile, frameassembly 52 included a tunnel 54 and an engine cradle 56 that wereriveted together. Because frame assembly 84, 190, 191 adds strength andrigidity to the overall construction and absorbs and redistributes manyof the forces encountered by the frame of the vehicle, the panels thatmake up the tunnel 86 and the engine cradle 88 need not be as strong oras thick as was required for the construction of frame assembly 52.

[0115] In the front of the vehicle, left and right shock absorbers 326,328 are connected to forward support assembly 134 so that the forcesexperienced by left and right shock absorbers 326, 328 are transmittedto frame assembly 84, 190, 191. In the rear of the vehicle, the left andright braces 122, 124 are orientated with respect to the rearsuspension. Upper column 118 is positioned close to the center ofgravity of the vehicle's sprung weight. The sprung weight equals all ofthe weight loaded onto the vehicle's entire suspension. The positioningof these elements such that they transmit forces encountered at thefront, middle and rear of the vehicle to an apex creates a very stablevehicle that is capable of withstanding virtually any forces that thevehicle may encounter during operation without sacrificing vehicleperformance.

[0116]Figure 35 illustrates the degree to which the rigidity of a frameconstructed according to the teachings of the present invention isimproved. The highest line on the graph shows that for a 100 kg load,the vertical displacement of the frame of the present invention is only-2 mm. However, in the prior art Bombardier ZX™ model snowmobile, a loadof only 50 kg produced a vertical displacement of -6 mm. In addition, aload of about 30 kg on the frame for the prior art Arctic Cat®snowmobileproduced a vertical displacement of -6 mm. In other words, thestructural rigidity of the frame assembly of the present invention isgreatly improved.

[0117] While the invention has been described by way of exampleembodiments, it is understood that the words which have been used hereinare words of description, rather than words of limitation. Changes maybe made, within the purview of the appended claims without departingfrom the scope and the spirit of the invention in its broader aspects.Although the invention has been described herein with reference toparticular structures, materials, and embodiments, it is understood thatthe invention is not limited to the particulars disclosed.

What is Claimed is:
 1. A frame assembly for a vehicle, comprising: atunnel; an engine cradle disposed forward of the tunnel, the enginecradle adapted to extend beneath an engine; and a rear brace assemblyextending forwardly and upwardly from the tunnel, the rear braceassembly comprising: a left leg having a front end and a rear end; and aright leg having a front end and a rear end, wherein the left leg andthe right leg extend forwardly and upwardly from the tunnel and the rearends of the left and right legs are spaced further from each other thanthe front ends of the left and right legs.
 2. The frame assembly ofclaim 1, further comprising an upper column extending upwardly from theengine cradle, wherein the upper column and the rear brace assembly forman apex above one of the engine cradle and the tunnel.
 3. The frameassembly of claim 2, further comprising a forward support assemblyextending rearwardly and upwardly, wherein the forward support assembly,the upper column, and the rear brace assembly form an apex above one ofthe engine cradle and the tunnel.
 4. The frame assembly of claim 3,wherein the forward support assembly comprises a first leg and a secondleg; and the left leg and the right leg of the rear brace assembly andthe first leg and the second leg of the forward support assembly form apyramidal structure
 5. The frame assembly of claim 1, furthercomprising: a forward support assembly extending upwardly, wherein theforward support assembly and the rear brace assembly form an apex aboveone of the engine cradle and the tunnel.
 6. The frame assembly of claim16, further comprising: a sub-frame disposed forward of the enginecradle and connected thereto; and a forward support assembly extendingrearwardly and upwardly from the sub-frame, the forward support assemblyincluding the second left leg and the second right leg, wherein thesecond left leg and the second right leg of the forward support assemblyand the left leg and the right leg of the rear brace assembly form anapex above one of the engine cradle and the tunnel.
 7. The frameassembly of claim 16, further comprising: an upper column extendingupwardly from the engine cradle, the upper column including the secondleft leg and the second right leg, wherein the second left leg and thesecond right leg of the upper column and the left leg and the right legof the rear brace assembly form an apex above one of the engine cradleand the tunnel.
 8. The frame assembly of claim 1, further comprising: anengine disposed in the engine cradle; an endless track operativelyconnected to the engine and disposed beneath the tunnel; and a pair ofskis operatively connected to a steering device.
 9. The frame assemblyof claim 1, further comprising: an engine disposed in the engine cradle;at least one rear wheel operatively connected to the engine and disposedbeneath the tunnel; and two front wheels operatively connected to asteering device.
 10. The frame assembly of claim 2, further comprising asteering bracket connected to at least one of the rear brace assemblyand the upper column, said steering bracket supporting a steering shaft.11. The frame assembly of claim 5, further comprising a steering bracketconnected to at least one of the forward support assembly and the rearbrace assembly, said steering bracket supporting a steering shaft. 12.The frame assembly of claim 6, further comprising a steering bracketconnected to at least one of the forward support assembly and the rearbrace assembly, said steering bracket supporting a steering shaft. 13.The frame assembly of claim 10, wherein the steering bracket includes aplurality of holes that selectively position the steering shaft in aplurality of positions.
 14. The frame assembly of claim 11, wherein thesteering bracket includes a plurality of holes that selectively positionthe steering shaft in a plurality of positions.
 15. The frame assemblyof claim 12, wherein the steering bracket includes a plurality of holesthat selectively position the steering shaft in a plurality ofpositions.
 16. The frame assembly of claim 1, further comprising asecond left leg and a second right leg, wherein the left leg and theright leg of the rear brace assembly and the second left leg and thesecond right leg of the frame assembly from a pyramidal structure whenviewed from above.
 17. The frame assembly of claim 7, further comprisinga steering bracket connected to at least one of the rear brace assemblyand the upper column, the steering bracket supporting a steering shaft.18. The frame assembly of claim 17, wherein the steering bracketincludes a plurality of holes that selectively position the steeringshaft in a plurality of positions.